feat(agents): add Hephaestus - autonomous deep worker agent (#1287)

* refactor(keyword-detector): split constants into domain-specific modules

* feat(shared): add requiresAnyModel and isAnyFallbackModelAvailable

* feat(config): add hephaestus to agent schemas

* feat(agents): add Hephaestus autonomous deep worker

* feat(cli): update model-fallback for hephaestus support

* feat(plugin): add hephaestus to config handler with ordering

* test(delegate-task): update tests for hephaestus agent

* docs: update AGENTS.md files for hephaestus

* docs: add hephaestus to READMEs

* chore: regenerate config schema

* fix(delegate-task): bypass requiresModel check when user provides explicit config

* docs(hephaestus): add 4-part context structure for explore/librarian prompts

* docs: fix review comments from cubic (non-breaking changes)

- Move Hephaestus from Primary Agents to Subagents (uses own fallback chain)
- Fix Hephaestus fallback chain documentation (claude-opus-4-5 → gemini-3-pro)
- Add settings.local.json to claude-code-hooks config sources
- Fix delegate_task parameters in ultrawork prompt (agent→subagent_type, background→run_in_background, add load_skills)
- Update line counts in AGENTS.md (index.ts: 788, manager.ts: 1440)

* docs: fix additional documentation inconsistencies from oracle review

- Fix delegate_task parameters in Background Agents example (docs/features.md)
- Fix Hephaestus fallback chain in root AGENTS.md to match model-requirements.ts

* docs: clarify Hephaestus has no fallback (requires gpt-5.2-codex only)

Hephaestus uses requiresModel constraint - it only activates when gpt-5.2-codex
is available. The fallback chain in code is unreachable, so documentation
should not mention fallbacks.

* fix(hephaestus): remove unreachable fallback chain entries

Hephaestus has requiresModel: gpt-5.2-codex which means the agent only
activates when that specific model is available. The fallback entries
(claude-opus-4-5, gemini-3-pro) were unreachable and misleading.

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

src/shared/AGENTS.md

@@ -1,7 +1,10 @@
 # SHARED UTILITIES KNOWLEDGE BASE
 
 ## OVERVIEW
-55 cross-cutting utilities: path resolution, token truncation, config parsing, model resolution.
+
+55 cross-cutting utilities. Import via barrel pattern: `import { log, deepMerge } from "../../shared"`
+
+**Categories**: Path resolution, Token truncation, Config parsing, Model resolution, System directives, Tool restrictions
 
 ## STRUCTURE
 ```
@@ -10,7 +13,7 @@ shared/
 ├── logger.ts              # File-based logging (/tmp/oh-my-opencode.log)
 ├── dynamic-truncator.ts   # Token-aware context window management (194 lines)
 ├── model-resolver.ts      # 3-step resolution (Override → Fallback → Default)
-├── model-requirements.ts  # Agent/category model fallback chains (132 lines)
+├── model-requirements.ts  # Agent/category model fallback chains (162 lines)
 ├── model-availability.ts  # Provider model fetching & fuzzy matching (154 lines)
 ├── jsonc-parser.ts        # JSONC parsing with comment support
 ├── frontmatter.ts         # YAML frontmatter extraction (JSON_SCHEMA only)